Glazing is usually done as the final step in making high quality confectioneries, to provide a brilliant surface and a moisture-barrier coating. Glazing is generally achieved using edible wax and/or shellac (Bertram, H. T., The Manufacturing Confectioner, 68(10):65-69 (1988). Shellac coating, in addition to giving a brilliant finish, provides very good protection against high humidity (Minifie, B. W., Chocolate, Cocoa & Confectionery: Science & Technology, 2nd Ed., AVI Publishing Company, Inc., Westport, Conn., pp. 105-127 (1980a). Shellac is a resinous secretion of the lac beetle and is refined to be used for the preparation of varnishes and polishes (Minifie, B. W., Science & Technology, 2nd Ed., AVI Publishing Company, Inc., Westport, Conn., p 252-273 (1980b). Prior to the glazing step, a gum solution is applied to seal the pores and cracks of the chocolate surface (Bertram, H. T., The Manufacturing Confectioner, 68(10):65-69 (1988); Strub, R., The Manufacturing Confectioner, 51-54 (1987). The main reason for the gum coating is to provide a barrier to the possible absorption of ethanol from the shellac coating solution into the chocolate. Ethanol, which is miscible with the fats and oils contained in chocolate, may cause bitter and off-flavors which are not desirable (Isganitis, D. K., The Manufacturing Confectioner, 68(10):75-78 (1988).
Using ethanol as solvent can also produce volatile organic compounds which are hazardous to the environment. Ethanol-based shellac also possesses a potential explosion hazard during processing (Minifie, B. W., Chocolate, Cocoa & Confectionery: Science & Technology, 2nd Ed., AVI Publishing Company, Inc., Westport, Conn., pp. 105-127 (1980a). A water-based glaze formulation would not only be able to eliminate one processing step (gum coating step), but it would also eliminate the potential explosion and environmental hazards. Additionally, many consumers would find elimination of an insect-based coating to be more palatable than an insect-based coating.
Whey proteins with plasticizer form transparent and flexible films when cast and dried from aqueous solution. A whey protein film using glycerol as a plasticizer was shown to provide high gloss, comparable to shellac, dextrin and corn zein and better than HPMC coatings, when coated on matte black acrylic plastic (Trezza, et al., J. Food Sci., 65(4): 658-662 (2000) (hereafter, “Trezza 2000”)). Unfortunately, when applied to chocolate rather than plastic, the whey protein-based film described in Trezza 2000 had a lower initial gloss value than it had had on plastic, and a rapid rate of gloss fade that resulted in the loss of gloss within a few days. It would be useful to have gloss coatings for confections and other foods that provide a higher gloss value and a gloss stable enough for use in normal commercial applications.
Another aspect of food acceptance by consumers is the freshness of peanuts and other nuts (although peanuts are technically legumes, they are considered as nuts in the mind of the public and are, for example, the predominant component of most so-called “mixed nut” products). Peanuts and other nuts are high in oil and fat content. In peanuts, for example, these oils and fats mainly consist of unsaturated fatty acid providing high vulnerability to oxidative rancidity (Conkerton and St. Angelo, Peanuts (Groundnuts), In: Wolff Iowa, editors, CRC Handbook of Processing and Utilization in Agriculture, Vol. 2, Part 2, Plant Products. Boca Raton, Fla. CRC Press, p 157-(1983); Yuki et al., J. Jpn. Soc. Food Sci. Technol., 25:293-301 (1978); Ahmed and Young, Composition, quality, and flavor of peanuts. In: Peanut Science and Technology, Amer. Peanut Res. & Educ. Assoc., Yoakum, Tex., p. 655-688). For roasted peanuts, autoxidation is the major cause of oxidative rancidity (Divino et al., J. Food Sci., 61(1):112-115, 120 (1996)). Autoxidation in peanuts results in ‘flavor-fade’ and off-flavor development, due to the masking of pyrazines by large amounts of low-molecular weight aldehydes such as hexanal (Warner et al., J. Food Sci., 61(2):469-472 (1996); Dimick, PS, Peanut flavor-fade research report, The manufacturing confectioner, Jan.: 45-48 (1994)). Hexanal, which is a major breakdown product of the linoleic acid oxidation (Frankel E N, Prog. Lipid Res., 22:1-33 (1982)), has been shown to be a good indicator of oxidative rancidity in peanuts (Mate et al., J. Agric. Food Chem., 44:1736-1740 (1996).
Whey-protein-isolate (WPI)-based films using heat denatured WPI have been found to be oxygen barriers (Mate and Krochta, J. Agric. Food Chem., 44(10):3001-3004 (1996a)). Whey protein coatings applied by a bench-scale coating method have been shown to provide some protection against oxidative rancidity in peanuts when analyzed by chemical and instrumental methods (Maté and Krochta, J. Food Sci., 61(6):1202-1206, 1210 (1996b); Mate et al., J. Agric. Food Chem., 44:1736-1740 (1996)). Application of whey protein films to peanuts, however, required viscous films, and achieving that viscosity required the whey protein mixture to sit for several days. It would be desirable to find improved methods for creating whey protein films that did not require materials to be prepared for days in advance of use.